Novel Ca doped Sr0.7Bi0.2TiO3 lead-free relaxor ferroelectrics with high energy density and efficiency

Sr0.7Bi0.2TiO3 with high relaxor behavior and energy storage efficiency (η) is expected to be applied in power energy storage capacitors. However, its energy storage density is limited by the relatively low dielectric breakdown strength (DBS). Herein, Sr0.7Bi0.2CaxTiO3 (SBT-xC, x = 0 ∼ 0.15) was prepared to decrease the average grain size of Sr0.7Bi0.2TiO3. This can effectively eliminate the oxygen vacancy and decrease the electrical conductivity and leakage current, which result in the enhanced DBS. Meanwhile, Ca doping increases the relaxor behavior and dielectric constant. When x = 0.1, the composition exhibits high DBS of 480.2 kV/cm and excellent energy storage properties, such as high energy storage density of 2.1 J/cm3 with high η of 97.6 % at 290 kV/cm, considerable thermal stability and great frequency stability. Moreover, SBT-0.1C shows high power density of 50.1 MW/cm3. These results suggest that SBT-0.1C is a potential candidate for high performance dielectric energy storage applications.